There are different R packages that provide users with general-purpose functions and specific techniques. This chapter introduces two powerful general purpose packages: data.table and plyr.

Some packages are already installed in the basic version of R. However, in order to use data.table and plyr, we need to download them from the official CRAN repository using install.packages. Let's start with data.table, which is a package that provides additional tools used to deal with data frames:

install.packages('data.table')

If the command doesn't work, you can specify the repository:

install.packages(
  pkgs = 'data.table',
  repos = 'http://cran.us.r-project.org'
)

After installing the package, we need to load it in order to use its functions. Unfortunately, R will import all the functions from the package without using a namespace, and sometimes there might be name conflicts across different packages:

library(data.table)

The package contains a new class called data.table, which...